Summary of Work: Lactoferrin gene that encodes a noneheme iron-binding glycoprotein serves as an ideal model to study the gene regulation at the molecular level. It is well documented that lactoferrin plays an important role in host defense, inflammatory response and immuno- modulation. The protein is expressed in a variety of tissues and biological fluids under different regulatory mechanisms. The lactoferrin gene is sensitive to estrogens; exnoestrogens and catecholestrogens, retinoic acid; glucocorticoid; forskalin and EGF. Therefore, environmental chemicals which perturb these signaling pathways could affect lactoferrin expression. The two transcription factors, ERRa1 and IKLF, isolated during the course of our present study, are involved in estrogen and EGF regulation of the lactoferrin gene expression, respectively. Characterization of these transcription factors is one step toward understanding the molecular events that are associated with the estrogen and EGF signalling pathways. - promoter, response elements, ERRa1, IKLF, mammalian two-hybrid system, HEC-1B and Jurkat cells